Carbon Pantograph Pads
Synopsis
Our client sourced carbon pantograph pads (used for collecting electrical current from the overhead line equipment) from three independent suppliers. The client was aware of apparent variability of in-service performance, both between the three and within batches from individual suppliers. The challenge was to review suppliers with the objectives of improving reliability, maximising service life, and delivering value for money. Tata Steel was appointed to carry out a physical investigation of samples of pads from each supplier, identify the reasons for variability in performance, and to make recommendations on the most suitable solutions for the client's needs. The client could then make future purchases on the basis of an independent and rigorous performance assessment.
Key Client Issues
The client needed to improve the reliability and increase service life of pantograph pads cost effectively. To do so the client needed to know:
- The differences in design and manufacture of the different pads to establish the contributory factors to the wear of pantograph pads, and how these could be controlled to increase their service life.
- Which supplier provided the best performing pads and which are the most cost effective?
Tata Steel was asked to undertake a project to investigate the performance of carbon pantograph pads from each supplier.
Solutions
The client supplied Tata Steel with information on the historical use of pads including stores withdrawal information on current and previous service trials, and financial information. Tata Steel carried out data analysis of this information along with meteorological information to identify trends in the use of pads and understand if there was any difference in the performance of pads from different suppliers.
A detailed examination of the pads from three manufacturers was carried out. Investigations included a study of wear behaviour and the condition of pads following removal from service, examination of new and worn pads and the effects of overhead line equipment on wear rates.
Tata Steel provided a report on the investigations into each supplier's carbon pantograph pads performance. Key outputs identified:
- That two suppliers were providing new pads containing large cracks, which lead to unpredictable wear rates and reduced service life.
- That one supplier's pads had a significantly higher wear rate than others, increasing costs.
- The best supplier in terms of in-service performance and lower wear rates.
- That weather has a significant effect on the performance of pads, especially in cold and wet conditions when arcing from the overhead line equipment significantly reduces the life.
Client Benefits
Our report enabled the client to:
- Purchase the most cost-effective pads from the suppliers with the best overall performance and wear rates.
- Stop using the least economic pads.
- Keep cost effectiveness of pads supply under continuing review.
- Potentially increase pad life by incorporating Tata steel's recommendations into a review of overhead line equipment. Potentially increase pad life by incorporating Tata Steel's recommendations into a review of overhead line equipment.
- Monitor the number of pads consumed from each supplier to inform purchase and renewal decisions.
